Abstract

Inclusion of London dispersion in density-functional calculations is now standard practice in computational chemistry and materials science. In this talk, we review how the dispersion energy can be written as an asymptotic series expansion from perturbation theory, which can be added to the self-consistent energy. We will then focus on the exchange-hole dipole moment (XDM) model, in which the dispersion coefficients are non-empirical and depend directly on the electron density and related properties. XDM offers simultaneous high accuracy for a diverse range of chemical systems, including molecular crystals, layered materials, and metal surfaces, without modification or reparameterization. A series of examples using XDM will be presented to clarify the difference between electronic and atomic many-body effects on the dispersion energy and to illustrate their relative importance. Applications to the chemistry of molecular crystals will be highlighted.